But you could apply the same names to the next full moon, which occurs Dec. 21, just 15 hours BEFORE the winter solstice. As the third full moon in a rare season with four, this one fits the original definition for a “Blue Moon.”
Popular usage has since attached the label to the second full moon in one calendar month.
The full moon falling on Sunday is a blue moon, at least by one definition of the term. This type of blue moon doesn’t come close to matching the popularity of the modern and trendy definition: the second of two full moons to occur in the same calendar month. This November full moon is still a blue moon, but for a different reason.
In an ironic twist, the newer and more famous definition for blue moon is thought to have originated from the less well known and somewhat antiquated definition: the third of four full moons in one season. A season refers to the time period between a solstice and an equinox — or vice versa. Most of the time, there are only three full moons in a season.